1. Field of the Invention
The present invention relates to a gas compressor of a vane rotary type for use in a car air conditioner system, and more particularly to a gas compressor in which vane back pressure can be reduced without degrading projectability of the vanes upon starting operation of the compressor.
2. Description of the Related Art
Conventionally, as shown in FIG. 10 and FIG. 11, in a gas compressor of such a vane rotary type, the interior of a cylinder 4 is partitioned into a plurality of small chambers by being defined by the cylinder 4, side blocks 5 and 6, a rotor 7, and vanes 12. Each of the thus partitioned small chambers functions as a compression chamber 13 for executing compression of a refrigerant gas.
That is, the volume of each compression chamber 13 alternately increases and decreases as the rotor 7 rotates, and a refrigerant gas in a suction chamber 14 is sucked up and compressed due to the variations in the volume and then discharged into a discharge chamber 15 side. In the course of such suction, compression, and discharge of the refrigerant gas, the vanes 12 slide within a vane groove 11 of the rotor 7 and is projected from the outer peripheral surface of the rotor 7 toward the inner peripheral surface of the cylinder 4.
Also, during the process of suction and compression, oil having a pressure lower than a discharge pressure Pd of the refrigerant gas is supplied as vane back pressure from scoop grooves 22, 23 of the front-side side block 5 and the rear-side side block 6 into the bottom portion of the vane groove 11. Then, the vanes 12 is pushed onto the inner peripheral surface of the cylinder 4 due to this vane back pressure and a centrifugal force generated by the rotation of the rotor 7.
Note that, when the process shifts from the compression of the refrigerant gas to discharge thereof, the pressure in the compression chamber 13 increases due to the pressure of the compressed refrigerant gas, and the increased pressure acts to push back the vanes 12 into the vane groove 11 so that the vanes 12 are moved away from the inner peripheral surface of the cylinder 4. To avoid this problem, the bottom portion of the vane groove 11 communicates with a high pressure supply hole 24 of the rear-side side block 6 at a time immediately before the discharge of the refrigerant gas, and then high-pressure oil having a pressure equivalent to the discharge pressure Pd is supplied as vane back pressure from the high pressure supply hole 24 into the bottom portion of the vane groove 11.
However, in the conventional gas compressor as described above, although the scoop grooves 22, 23 and the high pressure supply hole 24 are arranged separately from each other, as shown in FIG. 12, the scoop grooves 22, 23 and the high pressure supply hole 24 are communicated with each other via the vane groove 11 during the time when the vane groove 11 moves apart from the scoop grooves 22, 23 toward the high pressure supply hole 24 side. Thus, high-pressure oil flows into the scoop grooves 22, 23 side from the high pressure supply hole 24 via the vane groove 11, and the oil pressures within the scoop grooves 22, 23 are thus likely to increase. Therefore, the vane back pressure can readily rise upon starting the operation of the compressor, and the projectability of the vanes 12 is thus improved. However, during a steady operation of the compressor, the vane back pressure becomes excessively high, which results in such problems that not only is abrasion of the vanes 12 increased but also the power required for operating the compressor is increased.
The present invention has been made in view of the above problems, and therefore an object thereof is to provide a gas compressor in which power saving as well as improved compression performance and durability are attained by enabling reduction of the vane back pressure without degrading the projectability of the vanes upon starting the operation of the compressor.
In order to attain the above object, according to the present invention, there is provided a gas compressor comprising: a cylinder having side blocks attached to its end surface; a rotor rotatably disposed within the cylinder; vanes which slide within a vane groove that is formed on an outer peripheral surface of the rotor and which is arranged so as to be projectable from an outer peripheral surface of the rotor toward an inner peripheral surface of the cylinder; a compression chamber constituted by a small chamber that is partitioned off and defined in the interior of the cylinder by the cylinder, the side blocks, the rotor, and the vanes, which alternately increases and decreases in volume as the rotor rotates, and sucks in and compress a refrigerant gas in a low-pressure chamber due to the volume variation and then discharges it into a high-pressure chamber side; a scoop groove with which a bottom portion of the vane groove communicates during a suction and compression process of the coolant gas, and from which a vane back pressure is supplied into the bottom portion of the vane groove; a high pressure supply hole with which the bottom portion of the vane groove communicates at a time immediately before discharge of the coolant gas, and from which a vane back pressure having a pressure higher than that of the vane back pressure supplied from the scoop groove is supplied into the bottom portion of the vane groove; and a pressure control valve which interconnects the scoop groove with the low-pressure chamber side when there has occurred a reversed pressure relationship between the low-pressure chamber and the high-pressure chamber, wherein the scoop groove and the high pressure supply hole are arranged so as to be spaced apart from each other, and an interval therebetween is set to an interval sufficient to ensure that the vane groove is communicated with neither the scoop groove nor the high pressure supply hole during the time when the vane groove moves apart from the scoop groove toward the high pressure supply hole.
Therefore, since the present invention adopts the above structure, the vane groove is communicated with neither of the scoop groove and the high pressure supply hole during the time when it moves apart from the scoop groove toward the high pressure supply hole. Thus, it is possible to prevent a situation such that high-pressure oil flows into the scoop groove side from the high pressure supply hole side through the vane groove during a steady operation of the compressor. Further, when the operation of the compression is started, if there exists a reversed pressure relationship between the high-pressure chamber and the low-pressure chamber, the pressure control valve is actuated to introduce a relatively high pressure gas from the low-pressure chamber into the scoop groove side through the communication passage, thereby attaining an effect that the pressure within the scoop groove and the vane back pressure can readily rise upon starting the operation of the compressor.
According to the present invention, for the pressure control valve described above, there may be adopted a structure such that the pressure control valve includes: a communication passage communicating the suction chamber with the scoop groove; a hole having a shape of a circular truncated cone, which is arranged as a valve seat portion on a way of the communication passage; a valve body which is movably disposed within the communication passage and which is formed such that it may be fitted into the hole having a shape of a circular truncated cone; and a width extending means for partially extending a width of a minute gap between the valve body and the communication passage, in which when the pressure in the suction chamber has become higher than the pressure in the scoop groove, the valve body is moved apart from the hole having a shape of a circular truncated cone due to a pressure difference to thereby set the communication passage in an opened state, whereas when the pressure in the scoop groove has risen to exceed the pressure in the suction chamber, the valve body is pushed back into close contact with the hole having a shape of a circular truncated cone due to a pressure difference to thereby set the communication passage in a closed state.
For the pressure control valve described above, there may be adopted an alternative structure such that the pressure control valve includes: a communication passage communicating the suction chamber with the scoop groove; a hole having a shape of a circular truncated cone, which is arranged as a valve seat portion on a way of the communication passage; a valve body which is movably arranged within the communication passage and which is formed such that it may be fitted into the hole having a shape of a circular truncated cone; and a biasing means that constantly biases the valve body in a direction to move the valve body away from the hole having a shape of the circular truncated cone, in which when the pressure in the suction chamber becomes higher than the pressure in the scoop groove, the valve body is moved apart from the hole having a shape of a circular truncated cone due to a pressure difference to thereby set the communication passage in an opened state, whereas when the pressure in the scoop groove has risen to exceed the pressure in the suction chamber, the valve body is pushed back into close contact with the hole having a shape of a circular truncated cone due to a pressure difference to thereby set the communication passage in a closed state.
For the pressure control valve described above, there may be adopted an alternative structure such that the pressure control valve includes: a communication passage communicating the suction chamber with the scoop groove; a hole having a shape of a circular truncated cone, which is arranged as a valve seat portion on a way of the communication passage; a valve body which is movably arranged within the communication passage and which is formed such that it may be fitted into the hole having a shape of a circular truncated cone; a width extending means for partially extending a width of a minute gap between the valve body and the communication passage; and a biasing means that constantly biases the valve body in a direction to move the valve body away from the hole having a shape of the circular truncated cone, in which when the pressure in the suction chamber becomes higher than the pressure in the scoop groove, the valve body is moved apart from the hole having a shape of a circular truncated cone due to a pressure difference to thereby set the communication passage in an opened state, whereas when the pressure in the scoop groove has risen to exceed the pressure in the suction chamber, the valve body is pushed back into close contact with the hole having a shape of a circular truncated cone due to a pressure difference to thereby set the communication passage in a closed state.
According to the present invention, the following may be adopted as constituting the width extending means: 1) means for extending the width of the minute gap in an upper region thereof, out of the entire area of the minute gap; 2) means for extending the width of the minute gap at several locations; 3) a groove formed on an inner wall of the communication passage along a direction of movement of the valve body; 4) a groove formed on an outer peripheral surface of the valve body; and so on.
According to the present invention, a biasing force applied by the biasing means may be set to be greater than an adhesive force of an oil film to adhere the valve body to the hole having a shape of a circular truncated cone.